The present invention relates to flexible sheet dispensers for sequentially dispensing a web of material from a plurality of rolls, and in particular to an automatic transfer mechanism for transferring the feed supply from a working roll to a reserve roll, upon exhaustion of the working roll.
Industrial dispensers for toweling are primarily designed to dispense either a continuous length of web material, folded paper towels, or rolls of paper towels. Continuous towels are generally made of a reusable material and form a towel loop outside of the dispenser cabinet for the consumer to use. Folded towels are paper towels which are pre-cut and folded into various configurations to be individually dispensed for use. Roll towels are continuous rolls of paper toweling which are wound around a cardboard core and which are, upon dispensing, separated into and delivered as individual lengths of material.
Continuous web dispensers, such as those disclosed in U.S. Pat. No. 2,930,663 to Weiss and U.S. Pat. No. 3,858,951 to Rasmussen, require the user to pull on the loop of exposed toweling in order to cause a length of clean toweling to be dispensed and the exposed soiled toweling to be correspondingly taken up within the dispenser. Although economical, the continuous exposure of the soiled toweling is deemed unsightly, and therefore unacceptable to many consumers when compared to the many available alternatives. Further, the exposure and possible reuse of soiled toweling may present additional health hazards and sanitation concerns which should be avoided.
The use of either interfolded paper towels or C-fold paper towels eliminates the potential health risks associated with continuous web toweling. Dispensers for folded paper towels allow a user to pull the exposed end of a new individual towel in order to dispense the towel. These dispensers, such as the one disclosed in U.S. Pat. No. 3,269,592 to Slye et al., are also easy to refill with folded towels, That is, when the dispenser is partially empty, the cover can simply be removed and the remaining stack of towels can be replenished through the open top. Folded towels are, however, not usually the most economical alternative for institutional or other high-volume situations.
Roll towels are cheaper to manufacture than folded towels and also eliminate the potential health and sanitation problems associated with continuous web toweling systems. Dispensers for roll towels usually include a lever, crank, or other user-activated mechanism for dispensing a length of towel and a blade for then severing the length of towel from the remaining roll. In contrast to folded towels, however, there is no way to simply replenish a partially depleted roll of web material in a roll dispenser. In some prior art dispensers, a new roll must be substituted thereby resulting in the waste of the partially depleted roll, or xe2x80x9cstubxe2x80x9d roll. To overcome the problem of stub roll waste, roll dispensers have been designed to dispense two rolls of web material sequentially such that upon depletion of a primary roll, feeding from a reserve roll is commenced. Prior art systems have accomplished this transfer by either modifying the end of the web material or modifying the roll core upon which the web material is wound, such as the system disclosed in U.S. Pat. No. 3,288,387 to Craven, Jr. Alternatively, the system of U.S. Pat. No. 3,628,743 to Bastian et al. senses the diameter of the primary roll in order to activate the transfer to the reserve roll, and the system of U.S. Pat. No. 3,917,191 to Graham, Jr. et al. senses the tension in the primary roll in order to detect when it is nearly exhausted. Unfortunately, tension responsive transfers are not particularly reliable since conditions other than reaching the end of the roll can trigger their operation, such as the slackening of the web or a break in the web material. Diameter responsive transfers also have a drawback in that the reserve web begins dispensing prior to the complete exhaustion of the primary roll. Thus, for a short time web material is dispensed simultaneously from both rolls and again results in a waste of material.
To overcome these disadvantages, the systems of U.S. Pat. No. 4,165,138 to Hedge et al. and U.S. Pat. No. 4,378,912 to Perrin et al. provide a transfer mechanism which is based on the feed rolls themselves. These systems utilize a transfer mechanism which senses the absence or presence of paper around a grooved feed roll by using a sensing finger which rides along the top surface of the web material and which then drops down into the groove in the feed roll when the trailing end of the primary web has passed thereover and thus uncovers the groove. Responsive to the movement of the sensing finger into the groove, the reserve web is introduced into the feed nip between the feed rolls and dispensing from the reserve roll begins. This type of transfer mechanism generally eliminates the false transfer associated with tension responsive systems and reduces the amount of double sheet dispensing which occurs in other prior art diameter and end of roll responsive systems. The use of sensing fingers on the web material, can, depending on the design, produce extra friction which can inadvertently tear the web. Also, the introduction of additional components to sense the absence of the web and transfer the reserve web into the feed nip between the feed rollers creates additional opportunities for a transfer failure or interference with web feed to occur. In particular, in each of the designs of the Hedge et al. and Perrin et al. patents, a tucking device (blade or roll) is used. The device pivots into very close proximity to the feed nip, and remains there through the subsequent dispensing from the reserve roll. It is evident that interference with the web feed from the reserve roll could result if proper positioning of the transfer device, away from the nip, is not maintained.
A need has therefore existed for a flexible sheet dispenser having an automatic transfer mechanism which, in addition to substantially eliminating simultaneous dispensing from both primary and reserve rolls, requires few additional parts within the dispenser and which is not prone to interference with the proper dispensing of either the working or reserve roll web material. A transfer mechanism that, to a large extent, fulfills this need is described in commonly assigned U.S. Pat. No. 5,526,973 to Boone et al. Therein, movement and interengagement of one grooved feed roller relative to the other upon depletion of a stub roll, actuates a transfer mechanism that introduces a reserve web into the feed nip. While generally quite effective, the movement and spring biasing of a relatively high mass feed roller can lead to difficulties. The feed roller spring bias force must be within a relatively narrow window. If the spring bias is set too high, the biasing force may inhibit smooth feeding of the web material through the rollers, and result in tearing of the web material. If it is set too low, the mechanism may not actuate effectively to cause a transfer of feed to the reserve roll immediately upon depletion of the stub roll. Over time, the spring bias provided to move one roll relative to the other is prone to eventually decrease, e.g., due to fatigue of the spring, such that ultimately the spring force may fall below the required relatively narrow range and thus be insufficient to properly actuate a web transfer. There thus remains a need for an automatic web transfer mechanism that can provide increased reliability, robustness and cost effectiveness.
In view of the foregoing, it is a principal object of the present invention to provide a web transfer mechanism for a flexible sheet dispenser having increased reliability, robustness and cost effectiveness.
It is a further object of the invention to provide a web transfer mechanism which permits simple set-up/loading of the dispenser for sequential dispensing from a working roll and then a reserve roll.
It is another object of the present invention to provide a web transfer mechanism that avoids double feeding of web from the reserve roll and working (stub) roll.
A further object of the present invention is to provide a web transfer mechanism which is removed from the web feed path about the feed roll, such that post-transfer interference with web feed from the reserve roll is reliably avoided.
These and other objects are achieved, in accordance with a first aspect of the present invention, by a web transfer mechanism for providing, in a flexible sheet material dispenser, automatic transfer of web feed from a working roll to a reserve roll. A pair of feed rollers forms a nip for receiving a leading end of a sheet material web. A first one of the feed rollers includes at least one circumferential groove. A first arm is movably mounted adjacent and to one side of the first feed roller. The first arm includes a web transfer finger. The finger is movable into contact with a leading end portion of a sheet material web from the reserve roll positioned on the one side of the first feed roller, to a transfer position close enough to the first feed roller to move the leading end portion into the vicinity of the nip such that upon driving of the rolls the web is carried through the nip and along a path avoiding subsequent contact of the web with the finger. A second arm is movably mounted adjacent and to a second side of the first feed roller. The second arm includes a web sensing finger biased toward the feed roller into a web-present sensing position wherein the sensing finger rides lightly upon the surface of a sheet material web as it passes around the first feed roller, and such that when no sheet material web is present the sensing finger moves into a no-web-present position within one of the circumferential grooves. A stop arm is movably connected to the second arm. The second arm is capable of assuming a stop position preventing the web transfer finger from moving into the transfer position when the web sensing finger is in the web-present sensing position. The stop arm is movable with the second arm to a release position allowing the web transfer finger to move into the transfer position when the second arm moves into the no-web-present position.
A second aspect of the invention is likewise embodied in a web transfer mechanism for providing, in a flexible sheet material dispenser, automatic transfer of web feed from a working roll to a reserve roll. A first one of a pair of feed rollers forming a nip for receiving a leading end of a sheet material web includes at least one circumferential groove with serrations formed in a sidewall thereof A web transfer arm is movably mounted adjacent the first feed roller. The arm is movable into contact with a leading end portion of a sheet material web from the reserve roll, positioned on a side of the first feed roller, to a transfer position close enough to the first feed roller to move the leading end portion into the vicinity of the nip such that upon driving of the feed rollers the web of the reserve roll is gripped by the first feed roller, assisted by the serrations, and carried through the nip.
The above and other objects, features and advantages of the present invention will be readily apparent and fully understood from the following detailed description of preferred embodiments, taken in connection with the appended drawings.